1. Field of the Invention
The present invention relates to a capacitor in which a first electrode, a dielectric layer having a stacked layer structure including a plurality of sublayers, and a second electrode are sequentially stacked, a method of producing the capacitor, and a semiconductor device and a liquid crystal display device that include the capacitor.
2. Description of the Related Art
As a technique for increasing the capacitance of a metal-insulator-metal (MIM) capacitor, a capacitor including Ta2O5, which has a high relative dielectric constant, has been studied. However, improvement in leakage current characteristics has not been satisfactorily achieved because of the physical properties of Ta2O5.
Consequently, HfO2, Al2O3, and stacked layers composed of these compounds whose relative dielectric constants are somewhat low but which have excellent I (current)−V (applied voltage) characteristics have been studied. Furthermore, stacked layer structures each including Al2O3 or the like having excellent leakage current characteristics and Ta2O5 having a high relative dielectric constant have also been studied.
A known structure of a dielectric layer of a capacitor is a structure in which a Ta2O5 sublayer is sandwiched between sublayers made of Al2O3, which is a currently commonly used material (see, for example, Tsuyoshi Ishikawa et al., “High-Capacitance Cu/Ta2O5/Cu MIM Structure for SoC Applications Featuring a Single-Mask Add-on Process”, IEDM 2002 (hereinafter referred to as “Document 1”)).
A capacitor including a dielectric layer having a multilayered structure (laminated structure) composed of a plurality of HfO2 sublayers and Al2O3 sublayers is also known (see, for example, Hang Hu et al., “High performance ALD HfO2—Al2O3 Laminate MIM Capacitors for RF and Mixed Signal IC Applications”, 2003 IEDM (hereinafter referred to as “Document 2”); Shi-Jin Ding et al., “RF, DC and Reliability Characteristics ALD HfO2—Al2O3 Laminate MIM Capacitors for Si RF IC Applications”, IEEE Trans-Electron devices Vol. 51, No. 6, June 2004 (hereinafter referred to as “Document 3”); and Shi-Jin Ding et al., “Evidence and Understanding of ALD HfO2—Al2O3 Laminate MIM Capacitors Outperforming Sandwich Counterparts”, IEEE Electron devices Letter Vol. 25, No. 10, October 2004 (hereinafter referred to as “Document 4”)).
In these capacitor structures, the leakage current characteristics can be improved. In particular, according to Documents 2 and 3, the leakage current density of such structures in a low-voltage range is about 5×10−9 [A/cm2], thus realizing a satisfactory characteristic.
According to Document 4, a dielectric layer having a stacked layer structure in which sublayers composed of Al2O3 (1 [nm])-HfO2 (12 [nm])-Al2O3 (1 [nm]) are repeated is more preferable than a dielectric layer having a stacked layer structure of Al2O3—HfO2—Al2O3. The former dielectric layer has preferable characteristics. More specifically, a leakage current density at a low voltage is 1×10−9 [A/cm2] and a voltage at which the leakage current starts to markedly increase is about 7 [V].
Furthermore, it is known that the leakage current characteristics are improved by laminating a plurality of crystallized HfO2 and Al2O3 sublayers (see Shi-Jin Ding et al., “Evidence and Understanding of ALD HfO2—Al2O3 Laminate MIM Capacitors Outperforming Sandwich Counterparts” IEEE EDL Vol. 25, No. 10, October).
In addition, a structure of a dielectric layer of a capacitor in which a Ta2O5 sublayer is sandwiched between HfO2 sublayers whose leakage current characteristics are improved by adding Si to HfO2 (see, for example, Japanese Unexamined Patent Application Publication No. 2004-79687).